Myositis Autoantibodies

The diagnostic criteria for dermatomyositis and polymyositis, formulated by Bohan and Peter over 30 years ago, are based on clinical evidence of muscle weakness together with electromyographic and histologic evidence of muscle damage as well as elevated serum muscle enzymes indicative of damage. While these criteria still form the foundation for the diagnosis, it has become increasingly clear that patients with autoimmune myopathies frequently harbor myositis specific antibodies (MSA), each having a unique clinical phenotype. New autoantibodies are continually being identified and, to date, around 60-80% of patients with autoimmune myopathy seem to have at least one MSA. In fact, several classification schemes have proposed that the presence of MSA be included in inclusion criteria for dermatomyositis and polymyositis.